[clang] [MinGW] Set a predefined __GXX_TYPEINFO_EQUALITY_INLINE=0 for MinGW targets (#96062)

libstdc++ requires this define to match what is predefined in GCC for
the ABI of this platform; GCC hardcodes this define for all mingw
configurations in gcc/config/i386/cygming.h.

(It also defines __GXX_MERGED_TYPEINFO_NAMES=0, but that happens to
match the defaults in libstdc++ headers, so there's no similar need to
define it in Clang.)

This fixes a Clang/libstdc++ interop issue discussed at
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110572.

Author: mstorsjo

clang/lib/Frontend/InitPreprocessor.cpp

@@ -934,6 +934,12 @@ static void InitializePredefinedMacros(const TargetInfo &TI,
   if (LangOpts.GNUCVersion && LangOpts.CPlusPlus11)
     Builder.defineMacro("__GXX_EXPERIMENTAL_CXX0X__");
 
+  if (TI.getTriple().isWindowsGNUEnvironment()) {
+    // Set ABI defining macros for libstdc++ for MinGW, where the
+    // default in libstdc++ differs from the defaults for this target.
+    Builder.defineMacro("__GXX_TYPEINFO_EQUALITY_INLINE", "0");
+  }
+
   if (LangOpts.ObjC) {
     if (LangOpts.ObjCRuntime.isNonFragile()) {
       Builder.defineMacro("__OBJC2__");

clang/test/Preprocessor/predefined-win-macros.c

@@ -116,6 +116,7 @@
 // CHECK-X86-MINGW: #define WINNT 1
 // CHECK-X86-MINGW: #define _WIN32 1
 // CHECK-X86-MINGW-NOT: #define _WIN64 1
+// CHECK-X86-MINGW: #define __GXX_TYPEINFO_EQUALITY_INLINE 0
 
 // RUN: %clang_cc1 -triple thumbv7-windows-gnu %s -E -dM -o - \
 // RUN:   | FileCheck -match-full-lines %s --check-prefix=CHECK-ARM-MINGW
@@ -125,6 +126,7 @@
 // CHECK-ARM-MINGW: #define WINNT 1
 // CHECK-ARM-MINGW: #define _WIN32 1
 // CHECK-ARM-MINGW-NOT: #define _WIN64 1
+// CHECK-ARM-MINGW: #define __GXX_TYPEINFO_EQUALITY_INLINE 0
 
 // RUN: %clang_cc1 -triple x86_64-windows-gnu %s -E -dM -o - \
 // RUN:   | FileCheck -match-full-lines %s --check-prefix=CHECK-AMD64-MINGW
@@ -134,6 +136,7 @@
 // CHECK-AMD64-MINGW: #define WINNT 1
 // CHECK-AMD64-MINGW: #define _WIN32 1
 // CHECK-AMD64-MINGW: #define _WIN64 1
+// CHECK-AMD64-MINGW: #define __GXX_TYPEINFO_EQUALITY_INLINE 0
 
 // RUN: %clang_cc1 -triple aarch64-windows-gnu %s -E -dM -o - \
 // RUN:   | FileCheck -match-full-lines %s --check-prefix=CHECK-ARM64-MINGW
@@ -145,6 +148,7 @@
 // CHECK-ARM64-MINGW: #define _WIN32 1
 // CHECK-ARM64-MINGW: #define _WIN64 1
 // CHECK-ARM64-MINGW: #define __GCC_ASM_FLAG_OUTPUTS__ 1
+// CHECK-ARM64-MINGW: #define __GXX_TYPEINFO_EQUALITY_INLINE 0
 // CHECK-ARM64-MINGW: #define __aarch64__ 1
 
 // RUN: %clang_cc1 -triple arm64ec-windows-gnu %s -E -dM -o - \
@@ -157,6 +161,7 @@
 // CHECK-ARM64EC-MINGW: #define _WIN32 1
 // CHECK-ARM64EC-MINGW: #define _WIN64 1
 // CHECK-ARM64EC-MINGW: #define __GCC_ASM_FLAG_OUTPUTS__ 1
+// CHECK-ARM64EC-MINGW: #define __GXX_TYPEINFO_EQUALITY_INLINE 0
 // CHECK-ARM64EC-MINGW-NOT: #define __aarch64__ 1
 // CHECK-ARM64EC-MINGW: #define __amd64 1
 // CHECK-ARM64EC-MINGW: #define __amd64__ 1